Systemic Sclerosis (SSc) is a chronic disease characterized by extensive fibrosis, microvascular fibrointimal proliferation and autoantibody production. T cells and monocytes infiltrate early skin lesions of patients with SSc. We have demonstrated that skin-biopsies in five of five patients with SSc contain oligoclonal populations of T cells. Hemopoeitic fetal cells have been identified in women with SSc who had previously been pregnant. Activation of these fetal T cells in the mother results in clinical disease designated as maternal SSc, which resembles GVHD. Microchimerism of maternal cells has been identified in women who have not been previously pregnant or in men. Activation of these maternal T cells results in offspring SSc. The hypothesis to be tested in this RO1 application is: (a) whether T-cells infiltrating skin-biopsies from patients with maternal SSc are of fetal origin and whether their recognize alloantigens of maternal origin, by the direct or the indirect antigen recognition pathways; (b) whether T-cells infiltrating skin-biopsies from patients with offspring SSc are of maternal origin and whether their recognize alloantigens of offspring origin, by the direct or the indirect antigen recognition pathways. Our specific aims are: 1. To determine whether fresh (not expanded in culture) T cells infiltrating skin-biopsies from patients with maternal SSc or offspring SSc contain substantial proportions of monoclonal T cells. To determine whether these clonally expanded T cells are of fetal origin in maternal SSc or of maternal origin in offspring SSc. 2. To identify the antigens recognized by T cells employing the clonally expanded alpha- and beta-chain TCR transcripts in maternal SSc or offspring SSc skin-biopsies. a. To express the clonally expanded in SSc skin-biopsies TCR transcripts into ap TCR-negative J.RT3T3.5 Jurkat cells by transfection, or into normal CTL by infection with retroviral vectors. b. To determine whether these transduced or transfected T cells with the clonally expanded TCR, recognize alloantigen by the direct or the indirect recognition pathway. 3. To develop by limiting dilution T-cell clones specific for alloantigens or for putative SSc antigens (CMV and DNA topoisomerase I) from the same SSc patients studied in specific aim #1. a. To determine whether these T-cell clones are of fetal origin in maternal SSc or maternal origin in offsping SSc. To determine whether they recognize alloantigen. b. To characterize these T-cell clones phenotypically and functionally and to determine whether they recognize: (i) alloantigens; by the direct or the indirect recognition pathway; (ii) the putative SSc antigen(s) listed above. To determine whether these T-cell clones exhibit suppressor activity to allospecific responses or to CTL activity. c. To compare the TCR sequences utilized by these antigen-specific T-cell clones to those of fresh (not expanded in culture) SSc infiltrating T cells from the same patients, in order to determine whether clonal. populations of these fresh infiltrating T cells have the same antigenic specificities to those of antigen-specific T-cell clones. d. To identify Thl, Th2, suppressor, anergic and CTL T-cell clones from those developed above, on the basis of expression patterns of their genes, using DNA array technology.